Incompatible blend of polyurethane(PU) and nylon 66 was prepared from melt mixing method utilizing twin screw extruder, and screw speed was changed to enhance the compatibility of the blend. Tensile, impact, thermal properties were measured to evaluate the effect of screw speed change on the mechanical properties. Also morphological and structural behavior were analyzed from XRD and SEM. As the screw speed increased, the dispersed phase particle size decreased and the degree of dispersion improved, and resulted in an improved tensile and impact strength. More specifically, tensile strength of 25 wt% PU/75 wt% nylon 66 blend was 38.1 MPa at the screw speed of 100 rpm, and it increased to 50.3 MPa at 400 rpm. Strain at break of 75 wt% PU/25 wt% nylon 66 blend increased from 64.9% at 100 rpm to 141.7% at 400 rpm, thus showed more than 100% increase in strain at break. Impact strength of 50 wt% Pu/ 50 wt% nylon 66 and 25 wt% PU/75 wt% nylon 66 blend also showed a slight increase with the screw speed increase.